An integrated circuit (IC) is typically manufactured by a process which utilizes planar technology. Generally, this process includes growing a layer of silicon dioxide on a silicon wafer. Selected areas of the silicon dioxide layer are then removed by an etching procedure in which the selected areas are exposed to hydrofluoric (HF) acid. The etching procedure creates openings in selected areas of the silicon dioxide layer and exposes the underlying wafer. The silicon dioxide layer serves as a barrier to dopants that are used for forming a desired device or circuit. As such, removal of selected areas of the silicon dioxide layer forms a mask pattern which enables dopants for forming a desired device or circuit to be diffused into the exposed silicon. Typically, the silicon wafer is divided into a plurality of adjacent die. An IC is then formed in each die, thus enabling large quantities of IC's to be formed simultaneously and batch processed.
Selected dies are tested during the manufacturing process to ensure that various electrical characteristics meet acceptable standards before further processing is completed. Such characteristics include resistance, current gain and voltage breakdown. In order to conduct such in-process testing, selected areas of the silicon dioxide layer are removed to provide access to a selected die for test equipment such as an electrical probe.
A clamp device is utilized to remove each selected area of the silicon dioxide layer. Referring to FIG. 1, a prior art manual clamp device 10 is shown as a partial cross section. The clamp device 10 includes an upper arm 12 and a lower arm 14. The upper arm 12 includes an upper clamping end 16 and an upper handle end 18. The upper clamping end 16 includes a vertical passageway 20 and an upper O-ring 22 having a center hole 24 which is aligned with the vertical passageway 20. The lower arm 14 includes a lower clamping end 26 having a lower O-ring 28 and an lower handle end 30. In use, a wafer 32 having a silicon dioxide layer 34 formed thereon is clamped between the upper 22 and lower 28 O-rings such that the silicon dioxide layer 34 contacts the upper O-ring 22.
In addition, the clamp device 10 includes a pivot member 36 having a pivot pin 38 located in an upper portion of the pivot member 36. The upper arm 12 is rotatably secured to the pivot pin 38. The lower arm 14 is affixed to a lower portion of pivot member 36. As such, the upper arm 12 is able to rotate relative to the lower arm 14.
Consequently, referring to FIG. 1, the application of downward pressure on the upper arm 12 and upward pressure on the lower arm 14 on areas to the left of the pivot pin 38 will cause the upper clamping end 16 to rotate counterclockwise toward the lower clamping end 26. This compresses the upper 22 and lower 28 O-rings against the wafer 32, thus clamping the wafer 32. Consequently, a seal is formed between a selected area on the silicon dioxide layer 34 defined by the upper O-ring 22 and the remaining area on the silicon dioxide layer 34 outside of the selected area. An elastic element (not shown) is affixed to the upper 12 and lower 14 arms and to the left of the pivot pin 38. The elastic element serves to apply the downward and upward pressures described above for clamping the wafer 32. It is noted that the wafer 32 may also be clamped by applying an upward pressure on the upper arm 12 and an opposite downward pressure on the lower arm 14 on areas to the right of the pivot pin 38.
Conversely, the application of downward pressure on the upper 12 arm and upward pressure on the lower arm 14 on areas to the right of pivot pin 38, such as on the upper 18 and lower 30 handles, will cause the upper clamping end 16 to rotate in clockwise direction away from the lower clamping end 26, thus releasing the wafer 32.
In use, the operator visually scans the silicon dioxide layer 34 to locate a predetermined area that is to be etched. The operator then squeezes the upper 18 and lower 30 handles together, separating the upper 16 and lower 26 clamping ends and forming gap for receiving the wafer 32. The operator then positions the selected area on the silicon dioxide layer 34 which is to be etched within center hole 24 of the upper O-ring 22. The upper 18 and lower 30 handles are then released, thus causing the elastic element to rotate the upper clamping end 16 and clamp the silicon wafer 32 such that the upper 22 and lower 28 O-rings are compressed and a seal is formed as described above. A predetermined amount of HF acid is then introduced into the vertical passageway 20 by the operator. The HF acid travels down the vertical passageway 20 to the silicon dioxide layer 34 where the HF acid is collected and contained within the center hole 24 of the upper O-ring 22. This enables etching and the subsequent removal of the silicon dioxide within the selected area.
However, this technique has several disadvantages. A disadvantage is that the elastic element provides insufficient pressure for maintaining suitable compression of the upper O-ring 22. This causes leakage of the HF acid past the upper O-ring 22 and onto the silicon layer 34, resulting in the undesirable removal of silicon dioxide from areas on the silicon dioxide layer 34 outside of the selected area and in ultimate damage to the silicon dioxide layer 34. Consequently, the operator must manually pull the upper 18 and lower 30 handles apart to provide additional compression in order to stop leakage of the HF acid. This compression must then be maintained during the entire etch procedure. This leads to operator fatigue, resulting in leakage of the HF acid and undesirable etching of the silicon dioxide layer 34 as described above.
In addition, as can be ascertained, maintaining the clamp device 10 in an upright position is substantially dependent upon the operator. As such, it is difficult for the operator to hold the clamping device 10 in a stable manner and simultaneously introduce the HF acid into the vertical passageway 20. Consequently, some of the HF acid is frequently spilled on the outside of the upper clamping end 16, which results in the HF acid traveling down the outside of the upper clamping end 16 and onto an area of the silicon dioxide layer 34 outside of the selected area and ultimately causing damage to the silicon dioxide layer 34. In addition, the repetitive nature of this manual technique may possibly lead to the development of muscle strains or physical ailments such as carpal tunnel syndrome and others, thus further diminishing an operator's ability to compress the upper O-ring 22 or to hold the clamp device 10 in a stable manner.
A further disadvantage is that this manual technique is time consuming since the positioning of the selected area within the center hole 24 of the O-ring 22 is largely dependent on operator skill. Moreover, this technique is time consuming since the entire procedure must be repeated for each area which is selected for etching.